[TR] '3a carb piston getting stuck....

[Randall]

> Just finishing up the process of putting the refreshed carbs back on the
> '3a.  All is going ok, except, the rear most piston get stuck in the dome
> when pushed up.  It gets stuck as well when the dome is off the carb body
> so it is not the needle alignment.  That appears to be good.  It looks
> like the dome may have been dropped and now a small ding in the near top
> side that has reflected inside the dome and this is where the piston is
> getting stuck ( evidence of minor scratches ).

> What can I do?

Get some "layout dye" (aka "machinists blue" aka "Dykem") and spray (or
paint) it onto the inside of the dome where you think it is rubbing.
Eg, https://goo.gl/qJCrT3

Push the piston up gently until it starts to bind, then remove it.  If you
are right about where it is rubbing, you'll see a white spot where it rubbed
off the blue.  Take a piece of fine abrasive cloth (or sandpaper) and sand
down the white spot a bit, then try again.  The fit is supposed to be pretty
tight, so only remove a little at a time.

The blue dye will rinse off easily with almost any solvent although it's
somewhat harder to get off your hands.  I often wind up with a blue left
thumb :) 

-- Randall